Braving the one-hundred degree heat, and looking like Brave Heart, Michael Heise lead a group that protested the brutal macing, arrest, & abuse of four young men on July 3 by the West Chester, PA police. He tells the sad story of what happened that night in this video.
All was going fine at the protest until the police stepped in to stop the bullhorning. See it for yourself:

In another video the same cop says that the 1st Amendment doesn't apply to bull horns. He says this at 11:50: http://youtu.be/Nkv_TfzxcvU